Antifungal

Sometimes, tiny things called fungi make us sick. They can cause an itchy foot or a sore on the skin.

Doctors give us special medicine to fight them. This medicine can be a cream for your skin. It can also be a pill you swallow. Some medicine goes into your blood to help your whole body.

Some medicines work by breaking the tiny walls of the fungi. When these walls break, the tiny things cannot stay alive. This helps you get better.

Some medicines are for your eyes or your mouth. You might need a doctor to help you get them. It is important to use them the right way.

Doctors want to make sure the medicine works well. They watch to see if the fungi change to fight back. Using medicine the right way keeps us healthy.

Fungi can cause many sicknesses. They can cause itchy feet or mouth sores. They can even cause very serious infections. Doctors use antifungal medicine to treat these problems. Some medicines are sold in stores. Most need a prescription from a doctor.

There are many ways to take this medicine. You can rub a cream on your skin. You can swallow a pill. Some medicine goes into the blood through a needle. Other medicine is put into the eye or the nose.

Different medicines work in different ways. Polyenes are a group of drugs. They stick to a part of the fungal cell called the membrane. This makes the membrane leak. When the cell leaks, it dies.

Azoles are another group. They stop the fungus from making ergosterol. This is a part that the cell needs to grow. Echinocandins work by stopping the fungus from making its cell wall.

Sometimes, fungi learn to fight back. This is called resistance. It happens when fungi change so the medicine does not work. This can be a big problem for health around the world.

Antifungal medicines are special drugs used to treat or prevent fungal infections. These infections, called mycoses, can range from itchy athlete's foot to ringworm. Some infections are much more serious, like candidiasis or cryptococcal meningitis. Most of these medicines require a prescription from a doctor. However, a few types can be bought over the counter at a store. Doctors must choose the right medicine for the right job. Using the wrong treatment might not help the person get better.

There are many ways to take these medicines depending on where the fungus is. If the infection is on the skin, a person might use a topical cream like terbinafine. For infections in the eye, a medicine called natamycin is used. Some medicines are swallowed as oral pills, like ketoconazole. If the infection is very deep, doctors might use an intravenous (IV) method. This puts the drug directly into the blood to spread quickly. Other ways include vaginal treatments or even putting medicine into the spinal fluid.

Different medicines work in different ways to stop the fungus from growing. One group is called polyenes, such as amphotericin B. These drugs stick to a part of the fungal cell called ergosterol. This makes the cell membrane leak, so the insides of the cell spill out. This causes the fungal cell to die. Another group is called azoles, which includes drugs like fluconazole. These stop the fungus from making the ergosterol it needs to build its membrane. Other groups, like echinocandins, stop the fungus from building its protective cell wall.

Scientists and doctors are always learning more about these drugs. As of 2021, researchers were developing new classes of antifungals in clinical trials. This means they are testing new medicines to see how well they work. It is important to be careful with these drugs because they can have side effects. For example, some can cause allergic reactions or interact with other medicines. Some medicines, like amphotericin B, can even be hard on the kidneys. Doctors must check carefully before starting oral treatments for nail diseases.

We can think of antifungal medicine like a specialized tool for a specific task. Just as you wouldn't use a hammer to fix a window, doctors don't use every drug for every fungus. Some fungi are even learning how to fight back against the medicine. This is called antifungal resistance. It happens when fungi change so the drugs no longer work. This is a big concern for health around the world. Even certain fungi, like Candida auris, have become very hard to treat.

Antifungal medications, also known as antimycotics, are pharmaceutical agents used to treat or prevent mycoses. Mycoses are infections caused by fungi. These infections can range from common skin conditions like athlete's foot and ringworm to serious systemic issues. Examples of serious infections include candidiasis, known as thrush, and cryptococcal meningitis. While some antifungals are available over the counter, most require a doctor's prescription. Using these drugs correctly is vital because the evolution of antifungal resistance is a growing global health threat.

Doctors choose a route of administration based on where the infection is located. For ocular infections in the eye, natamycin is currently the only available antifungal, though other agents can be compounded. If a fungal infection reaches the central nervous system, doctors may use an intrathecal route. This involves injecting medicine like amphotericin B into the spinal fluid because systemic options cannot reach the required concentration there. For skin infections like tinea pedis, topical treatments such as terbinafine are used. Vaginal infections like candida vulvovaginitis are often treated with intravaginal clotrimazole.

Systemic infections can be handled through oral or intravenous (IV) routes. Oral administration is common if the drug has good bioavailability, which means the body can absorb it well. For example, ketoconazole is used orally to treat coccidioidomycosis. If a drug has poor bioavailability, the intravenous route is a better option. An IV injection of amphotericin B allows the drug to reach the bloodstream and distribute quickly throughout the body. This method is particularly useful for treating coccidioidomycosis when oral absorption is not efficient.

Antifungals are categorized into several chemical classes based on how they work. Polyenes are a major class, including drugs like amphotericin B, nystatin, and natamycin. These molecules are amphiphilic, meaning they have both water-loving and fat-loving parts. Polyenes work by binding to sterols in the fungal cell membrane, specifically ergosterol. This binding changes the transition temperature of the membrane. It forces the membrane into a less fluid, more crystalline state. This causes the cell's contents, such as monovalent ions like potassium and sodium, to leak out. This leakage is a primary way the fungal cell dies.

However, polyenes can sometimes affect human cells. Animal cells contain cholesterol instead of ergosterol. At therapeutic doses, some amphotericin B may bind to cholesterol in animal membranes, which increases the risk of toxicity. For instance, amphotericin B is known to be nephrotoxic, meaning it can be harmful to the kidneys when given intravenously. The length of the polyene's hydrophobic chain affects this risk. As the chain is shortened, its ability to bind to sterols increases, which can also increase its binding to cholesterol.

Another large class is the azoles, which includes imidazoles like clotrimazole and triazoles like fluconazole. Azoles work by inhibiting the enzyme lanosterol 14α-demethylase. This enzyme is required to convert lanosterol into ergosterol. By blocking this process, azoles prevent the fungus from building its cell membrane. This leads to an accumulation of 14-α-methylsterols. This buildup disrupts the packing of phospholipids and impairs membrane-bound enzymes, which inhibits fungal growth. Other classes include allylamines, like terbinafine, which inhibit squalene epoxidase, and echinocandins, which stop the creation of glucan in the fungal cell wall.

Echinocandins, such as caspofungin and micafungin, are administered intravenously. They are particularly useful for treating resistant Candida species by inhibiting 1,3-Beta-glucan synthase. Scientists are also studying other types, such as triterpenoids like ibrexafungerp. As of 2021, many novel classes of antifungals were in clinical trials to improve performance. Despite these advancements, doctors must be careful with side effects. Some azoles can interact with other drugs, such as calcium channel blockers or antidepressants, by affecting the cytochrome P450 family of enzymes. This can cause the concentration of those drugs in the body to increase unexpectedly.

Antifungal resistance is a significant challenge for modern medicine. Resistance can happen naturally through genetic mutation or aneuploidy. It can also develop due to external pressures, such as the overuse of clinical antifungals or their use in agriculture. This is considered a "One Health" concern because environmental and host factors all play a role. The emergence of Candida auris is especially concerning. This pathogen can exhibit multi-class drug resistance and has caused outbreaks globally. Because of these risks, the World Health Organization has released a priority fungal pathogen list to track these resistant threats.